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MattCat15
MattCat15
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First thing I'm sorry if this question sounds too much beginner-ish. I don't major in electrical engineering so I may lack the basic knowledge.

I have been noticing that, while tuning my AM radio, nearly all stations have a "secondary frequency" that transmits the same audio as the advertised frequency. However, the quality of the audio is a little lower than the advertised frequency. For instance, the channel's advertised frequency is 675 kHz and I found the secondary frequency at 630 kHz. Another example is that main frequency at 549 kHz and secondary frequency at 729 kHz.

The pairs of main-secondary frequency do not seem to follow any patterns or rules. So my question is:

  • Is this on purpose (as a backup frequency or something else)?
  • If it's not on purpose, why does this happen?

More information: My radio is a basic consumer radio (Sony) with FM and AM (AM radio tuner is ranged from 531 kHz to 1602 kHz, with 9 kHz step between frequencies).

First thing I'm sorry if this question sounds too much beginner-ish. I don't major in electrical engineering so I may lack the basic knowledge.

I have been noticing that, while tuning my AM radio, nearly all stations have a "secondary frequency" that transmits the same audio as the advertised frequency. However, the quality of the audio is a little lower than the advertised frequency. For instance, the channel's advertised frequency is 675 kHz and I found the secondary frequency at 630 kHz. Another example is that main frequency at 549 kHz and secondary frequency at 729 kHz.

The pairs of main-secondary frequency do not seem to follow any patterns or rules. So my question is:

  • Is this on purpose (as a backup frequency or something else)?
  • If it's not on purpose, why does this happen?

First thing I'm sorry if this question sounds too much beginner-ish. I don't major in electrical engineering so I may lack the basic knowledge.

I have been noticing that, while tuning my AM radio, nearly all stations have a "secondary frequency" that transmits the same audio as the advertised frequency. However, the quality of the audio is a little lower than the advertised frequency. For instance, the channel's advertised frequency is 675 kHz and I found the secondary frequency at 630 kHz. Another example is that main frequency at 549 kHz and secondary frequency at 729 kHz.

The pairs of main-secondary frequency do not seem to follow any patterns or rules. So my question is:

  • Is this on purpose (as a backup frequency or something else)?
  • If it's not on purpose, why does this happen?

More information: My radio is a basic consumer radio (Sony) with FM and AM (AM radio tuner is ranged from 531 kHz to 1602 kHz, with 9 kHz step between frequencies).

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MattCat15
MattCat15
  • 151
  • 4

Why do AM radio stations have secondary frequencies?

First thing I'm sorry if this question sounds too much beginner-ish. I don't major in electrical engineering so I may lack the basic knowledge.

I have been noticing that, while tuning my AM radio, nearly all stations have a "secondary frequency" that transmits the same audio as the advertised frequency. However, the quality of the audio is a little lower than the advertised frequency. For instance, the channel's advertised frequency is 675 kHz and I found the secondary frequency at 630 kHz. Another example is that main frequency at 549 kHz and secondary frequency at 729 kHz.

The pairs of main-secondary frequency do not seem to follow any patterns or rules. So my question is:

  • Is this on purpose (as a backup frequency or something else)?
  • If it's not on purpose, why does this happen?